The present invention relates to an improved liquid jet recording apparatus which effects non-impact or non-contact recording by the application of a jet or liquid marking medium, for example, liquid ink, to a recording medium.
Heretofore, two types of recording apparatus have been known. The recording apparatus of one type employs a recording head of a contact recording system which comprises a hollow fountain pen, a ball-point pen or a similar member adapted to contact a recording medium to draw or delineate, for example, a line on the recording medium. In such a recording apparatus, in order to interrupt the recording operation, the recording head has to be moved up and down and, therefore, the following disadvantages are observed. In other words, in view of the contact recording system, wear of the pen point, interruption of supply of ink, ink clogging, a spoiled surface of a recording medium, dust present on the surface of the recording medium, the smoothness of the surface of the recording medium, etc. often provoke problems to be solved. In addition, due to the fact that the up and down movement of the recording head requires a mechanism for effecting this movement, the recording head employed has to be of a relatively great size and often constitutes a source of noise and is not suited for high speed recording of a line of not more than 0.2 mm. in line width.
The recording apparatus of the other type employs a recording head of a non-impact or non-contact recording system which comprises a light projecting head which projects a beam of light onto a recording medium which is a light sensitive sheet. This recording apparatus requires a dark room in which the exposed light sensitive sheet is developed and fixed chemically. Moreover, the use of the light sensitive sheet for the recording medium often constitutes a cause for an increase of the operating cost.
Liquid jet recording systems are known, and may be classified into two types according to the manner by which a jet of liquid ink is produced: One type is disclosed in U.S. Pat. Nos. 2,600,129 and 3,060,429, respectively patented on June 10, 1952 and on Oct. 23, 1962, and includes, as shown in FIGS. 1 and 2, supplying liquid ink from an ink reservoir 1 to a nozzle 3 so as to form a meniscus at the exit end of nozzle 3 by the use of a suitable pressure applying means (not shown), applying between the nozzle 3 and a ring electrode 4 coaxially spaced from the nozzle 3 a high voltage DC power or a high voltage DC pulse signal superposed with a high voltage DC power, respectively from a high voltage DC power source 6 or a combination of a high voltage DC power source 6 and a high voltage pulse genertor 7, so that droplets of liquid ink can be expelled successively from the exit end of the nozzle 3 towards a recording medium. Particularly, in the method shown in FIG. 2, the frequency of formation of the droplets is synchronized with the frequency of the high voltage DC pulse signal generated by the high voltage pulse generator 7.
The other type of known system is disclosed in U.S. Pat. No. 3,596,275, patented on July 27, 1971, and is such that, as shown in FIG. 3, liquid ink from the ink reservoir 1 is, after having been pressurized to several kg/cm.sup.2, for example, 4.2 kg/cm.sup.2, by a pressure applying means 2', expelled towards a recording medium. In this method, if an ultrasonic vibrator 9 coupled to the nozzle 3 is oscillated by an oscillator 10 positioned outside the ultrasonic vibrator 9 and electrically connected therewith, the frequency of formation of droplets to be jetted becomes synchronized with the frequency of the oscillation of the ultrasonic vibrator 9 which is, for example, 100 KHz.
Printers, recorders and facsimile recorders practicing either of the foregoing methods have heretofore been known. In those devices wherein the first mentioned system is employed, deflection electrodes are provided between the ring electrode and the recording medium for controlling the electric field, established between the deflection electrodes, in response to an intelligence signal from an intelligence signal source to enable the intelligence signal to be recorded on the recording medium. On the other hand, in those devices wherein the second mentioned system is employed the ring electrode acts as a charging electrode for controlling the electrostatic charge, carried by droplets to be jetted, in response to intelligence signals from an intelligence signal source, so that the direction of travel of the droplets can be controlled as they pass through a space between the deflection electrodes.